8190

• UCREFRP Catalog Number: 8190
• Author: Papoulias, D. and W. L. Minckley
• Title: Effects of Food Availability on Survival and Growth of Larval Razorback Suckers in Ponds
• USFW Year: 1992
• USFW - Doc Type: Transactions of the American Fisheries Society
• Copyright Material: YES

FEEDING BY LARVAL RAZORBACK SUCKERS
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0.1 0.3 0.5 0.7 0.1 0.3 0.5 0.7 0.1 0.3 0.5 0.7 0.1 0.3 0.5 0.7 0.1 0.3 0.5 0.7 0.1 0.3 0.5 0.7
A Invert. body width (mm) B Invert. body width (mm)
FIGURE 2.-Percentage numerical composition (A) and percentage biovolumetric composition (B) of invertebrate
body widths in ponds fertilized at high, medium, and low levels at Dexter National Fish Hatchery, New Mexico,
1985. Week is indicated in the upper right corner.
high- and medium-fertilization treatments by week
3 (Figure 4). Cladocerans also occurred in larvae
from low-fertilization ponds, but in low volumes.
In week 4, eggs dominated larval diets volumet-
rically in fertilized ponds and Cladocerans were
eaten even more voluminously in unfertilized
ponds. Thereafter, cladocerans and chironomids,
in shifting proportions and supplemented by nau-
plii and ostracods, accounted for most of the gut
volumes in all ponds.
In week 2, rotifers were the numerically domi-
nant invertebrate food of razorback sucker larvae
in all ponds (Figure 4). Diets then diversified over
the next 4 weeks. Beginning in week 4, cladocerans
increased steadily in numerical dietary impor-
tance and the amount of this increase was roughly
proportional to the amount of pond fertilization
that had occurred. Much of the gain in cladoceran
frequencies was at the expense of chironomids.
Toward the end of the study (weeks 6 and 7),
ostracods gained numerical importance to larvae
in low- and medium-fertilization treatments, and
copepods and eggs were eaten with modest fre-
quencies in highly fertilized ponds. 1
After week 2 when larvae measured about 11
mm TL, essentially all larval guts were full of food.
Logo (food volume) increased linearly with larval
size (rz = 0.54; Figure 5). However, logo (prey
number) remained relatively constant (r2 = 0.09)
as the size of larvae increased; thus, progressively
larger animals were eaten. Neither numbers (F =
2. 1, P = 0.12) nor volumes (F = 1.4, P = 0.26)
of items in guts differed among treatments for a
given size of fish. Treatment data were therefore
pooled for regressions.
Upper lip length (or the calculated gape) of lar-
vae increased linearly with increasing TL (Figure
6). The relationship of ULL to TL for larval ra-
High Medium Low
High Medium Low